The present invention is directed to printing sleeves for offset or flexographic printing, and more particularly to printing sleeves having a sound dampening feature that attenuates noise during mounting and dismounting of the sleeve from a support cylinder.
An offset printing unit has a plurality of rotatable cylinders, including at least one plate cylinder and at least one corresponding blanket cylinder. The plate cylinder carries a printing plate having a surface on which an inked image is defined. The blanket cylinder carries a printing blanket. The plate on the plate cylinder transfers the inked image to the blanket on the blanket cylinder at a nip between the plate cylinder and the blanket cylinder when the cylinders rotate. The blanket on the blanket cylinder subsequently transfers the inked image to the material being printed, such as a web of paper.
Printing blankets have conventionally been formed as flat sheets which are then mounted on a blanket cylinder by wrapping the sheet around the blanket cylinder. More recently, printing blankets in the form of hollow tubular sleeves have become more prevalent. Such sleeves are mounted on a blanket cylinder by sliding the sleeve telescopically over the blanket cylinder. The sleeve and the blanket cylinder are designed so that the sleeve is receivable over the blanket cylinder with an interference fit.
The blanket cylinder is equipped with air flow passages and openings to direct a pressurized flow of air over the blanket cylinder. When the sleeve is located over the air flow openings in the blanket cylinder, the pressurized flow of air expands the sleeve diametrically. The expanded sleeve can be moved axially onto, or off of, the blanket cylinder when in its expanded condition. When the pressure is relieved, the sleeve contracts diametrically against the blanket cylinder and thus establishes an interference fit with the blanket cylinder. Flexographic printing sleeves have also been developed and are mounted onto and dismounted from support cylinders in much the same manner as offset sleeves.
One problem with such sleeves is that the compressed air that is used in mounting and dismounting the sleeves from the cylinders can create a whistle or other loud noise during the procedure. The sleeve ends may also vibrate causing additional noise to emanate during mounting and dismounting. In some instances, press operators may need to don ear protection gear to avoid injury. One solution to the problem has been proposed by Vrotacoe et al, U.S. Pat. No. 5,215,013. Vrotacoe et al describe a blanket sleeve having a damping ring made of a resinous material that is adhered to the interior wall of the sleeve near and end thereof. The ring is designed to reduce vibrations caused by the flow of pressurized air and attenuate-noise associated with mounting and dismounting of the sleeves.
Another solution has been proposed by Boucher et al, U.S. Pat. No. 6,347,586 B1. Boucher et al adhere a sound dampening material on the outer surface of the blanket cylinder such that the material engages the interior wall of the printing sleeve during mounting and dismounting thereof. The preferred material for use is a non-woven, fibrous material such as the “hook” portion of a VELCRO® closure.
However, the proposed solutions have not been entirely successful in solving the problem. Accordingly, there remains a need in the art for a printing sleeve having a sound dampening feature that attenuates noise during mounting and dismounting of the sleeve from a support cylinder.